Abstract

The word “sustainability” means different things to different people. Sustainability is an umbrella framework within which systems may run with longevity, thereby improving the sustainability of the system. The problem facing most people is that of measuring sustainability. Sustainability measurement has been practiced by several studies, but this review revealed that many researchers are applying methodologies outside of a cohesive model. This paper evaluates sustainability measurement, audit frameworks, and methodologies in an engineering context thus creating a cohesive hierarchy for sustainability. The developed Integrated Sustainability Measurement Hierarchy (ISMH) clearly positions hierarchical sustainability measurement systems against an influence level framework that extends from product to global influences. The ISMH would provide insight as well as a guideline to help devise a comprehensive sustainability measurement system for better decisions at various influence levels.

Keywords:

1. Introduction

Sustainability means different things to different people. Sustainability is an umbrella framework within which systems may run with longevity, thereby improving sustainability of the system. The Bruntland Report “Our Common Future”[1] began the process of defining sustainable development and all that it embraced. Since its publication in 1987 many researchers have developed numerous sustainability approaches that consider frameworks, standards, audit methods and influence levels. Often the diversity and complexity of such approaches is the result of an isolated sustainability approach.

Basically, a measurement system has evolved and more intricate to be applied on a higher influence level. Therefore, an influence level is the most dominant factor in choosing a measurement system. It was seen necessary to consolidate approaches, selecting the most appropriate methodologies and systems for sustainable product development. In this paper, important literatures on the sustainability measurement are reviewed to analyze the correlation between sustainability measurement systems and influence levels. Most researchers use the Life Cycle Analysis (LCA) approach applying Embodied Energy as the base metric but others use specific outputs depending on the project. For example, sulphur output was used to determine the efficiency of catalytic convertor renovations. Cradle to Cradle (C2C) is an alternative approach but considered to be idealistic and therefore only used in theoretical studies. A comprehensive model for sustainability measurements, Integrated Sustainability Measurement Hierarchy (ISMH), is developed from the analyzed correlation. The amalgamated hierarchy of sustainability methodologies is closely linked to influence levels that range from influence of the product through to global influences. The ISMH would provide a guideline and insight to help devise a comprehensive sustainability measurement system for better decisions in various influence levels.

2. Overview of Frameworks

Research shows that various institutions, scientific bodies, researchers, etc., apply their work to one or a combination of the following frameworks: Triple Bottom Line (TBL), Life Cycle Analysis (LCA), Cradle to Cradle (C2C) and Environmental Standards.

TBL is an accountability framework with three elements: social, environmental and financial. These three divisions are also sometimes known as the 3P’s: people, planet and profit, or the “three pillars of sustainability”. Interest in TBL accounting has grown in for-profit, non-profit and government sectors. The term was coined by John Elkington in 1994. The Economist [2].

LCA is sometimes known as “cradle to grave analysis” and is an assessment technique relating to environmental influences from a product throughout its life-cycle. The analysis covers extraction of materials for production through manufacture, use and eventually disposal and offers a broad investigation with the possibility of a detailed analysis of environmental concerns.

C2C is an approach to the design of products and systems that views human industry in the same terms as cyclical natural processes. Materials are viewed as nutrients circulating in healthy, safe metabolic systems. The strategy suggests that industry must protect and enrich nature’s biological metabolism while also maintaining a safe, productive technical metabolism. It is an overall economic, industrial and social framework that promotes the creation of systems that are efficient and waste free. The model can be applied to many aspects of human civilization such as urban environments, buildings, economics and social systems. C2C is a registered trademark of McDonough Braungart Design Chemistry consultants and the phrase “Cradle to Cradle” was originated by Stahel in the 1970s.

Standards and eco-labels often form the basis of an environmental approach and are usually issued depending on the industry and the environmental system. The most useful standards are often considered to be the ISO14000 series since their combination of broad management approach and detailed analysis is relevant for many sectors.

Several ISO standards have been considered and proved to be particularly useful in setting out the LCA approach. These included: Eco-design Directive ISO 14006 - 2011[3], ISO14040 - 2009 Environmental management[4], ISO14044: 2006: Environmental Management LCA Requirements[5] and PAS2050: 2011: Specification for the Assessment of Life Cycle Greenhouse Gas Emissions of Goods and Services[6]. Many of the references dealt with very specific topics, such as PAS 2050[6] which considered greenhouse gas emissions, but, were helpful in showing different ways to approach sustainability analysis. These standards cover many aspects of environmental attentiveness and can be used for many diverse environmental situations.

2.1 Framework Evaluation

Audit and measurement have become the focus of many researchers, institutions, and nations but the adage, “measure it to manage it” is very relevant. Measurements take many forms depending on the system and may use precise measurements such as carbon emission or energy usage. A more global assessment may use trends and indices that incorporate a variety of measurements.

These sustainability measurement approaches are championed by several researchers. Ameta[7] presents recent trends in design for sustainability from a strategic point of view and uses LCA and TBL as a background framework. He suggests that clear system boundaries are critical for proper auditing and measurement and that the use of indices are only one measurement device. He also suggests that there are several weaknesses with indices relating to weighting, aggregation and comparisons which dilute the quality of the data. Alternatively, he suggests direct measurement such as that of energy usage or Sulphur emission.

Chapas[8] champions the use of LCA in the sustainability design process to allow the LCA to be segmented into individual life elements. Mayyas[9] also supports the use of the LCA as a framework combined with TBL, thus broadening the scope into environmental, social and economic realms. A product sustainability methodology is put forward by Shuaib[10] who extensively uses LCA, TBL and the range of environmental standards within the ISO 14000 series. The approach employs life cycle phases to obtain a detailed analysis. The model produces a sustainability index (Prod SI) which is then applied to the TBL thus broadening the approach to influence economic, social and environmental features. This a step forward in applying the model but does not define measurement methods and omits major elements such as sustainable design, maintenance practices and end of life disposal.

Practitioners within the built environment have made major contributions to sustainable products and LCA. Hernandez[11] suggested a life-cycle approach to new buildings using embodied Energy as a measurement parameter but this was quickly converted to kilowatt*Hour and then to cost. The adopted life cycle considered only part of the total life cycle including only procurement, building and usage, and permitting maintenance and end of life disposal. Hacking [12] provides a general assessment framework based on the TBL and is intended for the global analysis rather than a detailed analysis, but nevertheless champions a most useful framework tool.

C2C is a relative newcomer to the framework analysis stable. Anders[13] explained that C2C attempts to increase the positive footprint whilst LCA attempts to decrease the negative environmental footprint. C2C eliminates the concept of waste suggesting the design of systems with waste that other processes can take up as nutrients. Anders criticizes the C2C model explaining that the C2C concept is idealistic and impractical since it disregards waste disposal and energy needs. He goes on to suggest that though LCA is more practical, it does not contain any long-term vision strategy.

LCA has been used and applied by many other researchers. Researchers such as Landolfo[14], Ashby M[15], Granta Design[16], Heiskanen[17], Hauschild[18] and Wanyama[19] all put forward LCA as an appropriate framework to assess sustainability and covered the use of sustainable materials through sustainable manufacturing and management.

2.2 Sustainability Assessment and Framework

Many projects require means of measuring, auditing, managing and implementing the principles of sustainability that can be used at the detail level in the design of new products. This practical approach requires a practical framework. The basic choice lying between LCA and C2C. The work presented by Chapas[8], Mayyas[9] and Shuaib[10] suggested that work at the detail level would be best served by a framework of LCA. They suggested that the combination of LCA with TBL and various standards would serve as a complete system using specific data at the detail level and combining it with a wider approach thereby expanding the data into a more global viewpoint incorporating sustainability, economy and society. Ness[20] uses a simile for TBL but nevertheless successfully combines data acquisition using LCA with TBL to create global indicators at various influence levels. Additionally, the application of environmental standards e.g. ISO14001[21,22] and others in this series, would ensure appropriate management, recording and systemic application.

3. Review of Auditing and Measurement Techniques

Sustainability measurement techniques should be reviewed to ensure applicability and to ensure the data is in a usable format. Auditing and measurement techniques are varied and complex. Some researchers use specific measurements of energy usage, carbon dioxide output, Sulphur emission, etc. Kizilboga[23] investigated the sustainability (environmental efficiency) of catalytic convertors using Sulphur output as a measure of efficiency. Other researchers prefer to use indices and trends. The focus of these measurements and eventual use may be as varied as compliance with standards, environmental impact, ecological sustainability, systemic preservation or global sustainability.

Ness[20] provides a sustainability assessment framework loosely based on the TBL and incorporating detailed product analysis from LCA which is then expanded into cost pressures on one side of the model to global indicators on the opposite side of the model. His three main columns are shown in Fig. 1 alongside the TBL for comparison.

Ness attempts to categorize the varied elements which contribute towards sustainability appreciation. Whilst some of the features comply with and contribute to the thinking of other researchers in the use of LCA and TBL, the model can be seen to be a tool that combines indices, useful for urban, national, continental and global assessments. Useful elements are those such as the use of LCA, system dynamics applications and use of standards.

A major contribution to simplifying the complex measurement process was made by Jamtsho[24], who was primarily concerned with sustainable audit practice. He succinctly described five audit categories: compliance, systems, environment, ecological and sustainability. Though Jamtsho’s model is concerned with auditing, the suggested system and practice includes some fundamental building blocks useful for sustainability measurement.

Moles[25] suggested that sustainable development was a process by which a current system was moved from the present towards a future sustainable situation in his work on urban environments. He used 174 indicators to judge the urban pulse of several townships and his measurements included energy usage, carbon dioxide emission, food tonnage, cost of living, waste, water, transport costs, etc. These indicators were combined into several classes of indices and translated to an ecological index. It is significant that Moles realized that the measurement of sustainability in a complex urban environment requires complex data acquisition which requires manipulation into an understandable index and recognize that manipulation of the data could lead to the resulting index becoming diluted being influenced by subjective weightings.

The complexity of sustainability auditing and measurement leads many researchers to use indices and trends. Much of the primary information used in indices was at some point a quantified value, however, the aggregation and combination of the data into an index tends to dilute the information. Concerns were addressed by Moles and several other researchers including Ameta[7], Singh[26], Moran[27] and Babcicky[28].

Sustainability measurement grows as the focus expands from individual products to a more global view where there are few other means of judging the value of sustainability other than using an index. There are many notable organizations that successfully use indices including the United Nations, national governments, urban centers (cities and towns), companies and institutions such as universities. Neumayer[29] was concerned with human development and sustainability and attempted to link the Ecological Footprint (EF)[30] to the United Nations Human Development Index (HDI). This was a classic application of indices used at national, continental and global levels.

Pope[31] proposed that indices are created to assist in assessment strategies and lists several indices such as Strategic Environmental Assessment (SEA), Environmental Impact Assessment (EIA) and advocates the use of the TBL. Pope also agreed that as assessment focus shifted from detail design to more global issues, indices grew broader and inherently less accurate. He concluded that “nevertheless a carefully formulated index can be invaluable for considering multiple and complex variants.” He also proposed that a sustainability assessment should be evaluated for its accuracy and outcome before committing resources to a complete sustainability assessment suggesting a requirement for a clear concept of the sustainability goal defined by criteria against which the assessment is conducted.

Many researchers suggested that the complex nature of sustainability assessment requires ever more complex indices in the expansion from detailed assessment through urban, national to global assessment. Even though there are complications and problems, indices are a viable assessment method.

Antiohos[32] related his work in designing a new cement building material where the metric was Embodied Energy, measured in Joules. The outcome used Watt*Hour/kg as a base measurement which was then converted to a cost. The cost metric is often used as in the work of Marten[33] who endeavored to decrease the operational cost of high-performance oil field services in terms of the cost of components, systems and facilities.

The publication review confirmed the need for a detailed comprehensive sustainability measurement system at the product level and showed that most practical researchers used LCA as an applied framework. The information thus generated was used to create indices which fed into the broader umbrella framework of the TBL. There are other approaches such as C2C but these are deemed idealistic by Anders[13] and others. The work afforded by Chapas[8], Mayyas[9] and Shuaib[10] suggested that work at the detail level would be best served by a framework of LCA. These researchers also suggested that the combination of LCA with TBL and various standards would serve as a complete system.

A review of standards revealed that the ISO14000 series[4,5,20,21] were comprehensive and dealt with several aspects of application, measurement and management of sustainability also allowing seamless meshing within the set but also with other management software such as ISO9001 Quality Standard[34].

The complexity of sustainability measurement systems has led many researchers to use combined data in creating indices and trends. Indices are generally used for decision making in more global programs. Depending on the measurement process, device or situation, researchers used specific measurement systems. Antiohos[32] applied Embodied Energy (Joules) to building materials whilst Kim[35] applied economic outcomes but used Watt*Hour/kg (Joules/kg) as a base measurement. Cost metrics are often used. The work of Martin and Gatzen[33] reviewed operational costs of oilfield services where the metric was US dollars.

Several researchers working at a practical level have applied Embodied Energy as a sustainability measure. Ashby[15] and Ashby[36] measures Embodied Energy across the product life-cycle. This is a metric which has been adopted by researchers who work on detailed analysis of products and systems including, Mayyas[9], Pope[31], and Hernandez[11]. The use of Embodied Energy as a metric efficiently lends itself to measure activity within all the elements of LCA.

Often the measurement metric needs to span industries and needs to measure services as well as products and to generate a value for each life cycle element. Several metrics have been considered including carbon footprint, but the only measurement device that would fulfil the measurement requirements across the entire life cycle was that of Embodied Energy.

Many articles were concerned with the measurement of the effects and the drains on the environment. Datschefski[37] was the only researcher who suggested that the sustainability of a product may also be gauged by considering renewable energy and though this metric relates to the use of energy, he suggests that the energy generated by a product, such as wind generator, solar panel, etc., can be considered within the Embodied Energy tally.

Luttrop[38] and others such as Johnson[39], Pope[31], champion the design function as being the sole influencer across all aspects of the product life cycle requiring that practical data is fed back to the design function from all aspects of the product life cycle with subsequent product improvements. The use of the LCA framework allows the generated data to be fed back to the design function and to other elements of the product life cycle including the management team, hence modifying products and enhancing their function and sustainable efficiency.

Management of data control and material flow may be based on guidelines within ISO standards[3-5]. Such systems deal with the product but contribute to a wider brief such as TBL which is considered the most useful overview framework choice, engendering a practical approach whilst considering social, economic, and sustainability features. Ameta[7], Ness[20], Jamtsho[24] and Shuaib[10] are all proponents of TBL especially when linked to measurement systems and the LCA.

The measurement of sustainability, especially regarding new products, is relatively new but various institutions, scientific bodies, researchers and governments realize that effective decision-making requires some form of sustainability measurement. Often measurements are based on a specific output such as carbon or perhaps Sulphur, but the review showed general limitations in approaches to sustainability measurement. Some of the major findings are listed below:

∙ several sustainability frameworks were applied in isolation.

∙ some sustainability frameworks were shown to be idealistic.

∙ measurements were made either in a narrow band of information or isolated to a part of the life cycle.

∙ Information often remained at the investigation level rather than being used for wider decision-making requirements

There were many positive aspects being applied by researchers such as:

∙ the application of LCA, which was good for detailed analysis of products

∙ the application of the TBL used in higher level and broader decision-making

∙ the concept that product design is the key to entire product life cycle sustainability control

The review showed that many researchers are using Embodied Energy as a means of measuring sustainability but often the measurements are limited in practice, depth and detail. Many works have been accomplished by researchers, especially in recent years but there are several gaps which can be filled with the help of a cohesive and comprehensive sustainability measurement guideline. An integrated hierarchy is devised in this work to provide comprehensive perspectives on sustainability measurement systems. It should help to consolidate previous works and improve measurement techniques including enhancements to the product life cycle.

Fig. 2 summarizes the nature of the sustainability measurements systems across the influence levels. The diagram is synthesized from reviews of the publications in Section 3. There are as many metrics as there are systems being measured, and measurement is complicated further when considering the end use of the data and its inevitable manipulation into an index format. As the intended use of the data becomes more global, greater manipulation is required to give a broader picture but this very action dilutes the data. The complexity of many measurement systems requires computing algorithms to produce viable data that can be used and directed for decision-making processes.

Nature of the sustainability measurement system across influence levels

4.1 Influence Levels and Data Usage

Sustainability data is applied at various levels from the product design level through to global levels. Researchers such as Chapas[8], Mayyas[9] and Shuaib[10] have suggested a combination of LCA and TBL, though Ness[20] successfully combined the two frameworks. Fig. 3 shows the influence levels and the proponents of various inputs at each influence level.

Analysis of correlation between sustainable measurement systems and influence levels

It should be noted that pure data is often obtained at sub-framework levels and it is only when contextualized in an LCA framework that the data becomes useful. Data can be very specific such as Sulphur output but many researchers, mentioned above, and including ISO 14000 series[4-6] and Ashby[15] all propose that Embodied Energy is the most appropriate measurement value since it can be applied for any service and across all elements of the LCA

Fig. 3 shows that hard data in the form of Embodied Energy can be gleaned from the design function, products and systems and fed into the LCA for a product or system. Fig. 3 also shows how this view is supported by many researchers.

LCA is the receptor for Embodied Energy and can then influence and be applied directly at Company, Institution and Urban levels. To have influence at higher levels such as National, Continental and Global levels the TBL needs to be used in combination with the LCA data, which can then be further combined with other influence factors such as population growth or perhaps increased highway use, etc.

The TBL enables LCA data to be placed into appropriate categories and combined with other influence factors, thus creating a wider view for national, Continental and Global decision makers. It should be noted that mixing raw data with other influence data is necessary for high level influence decisions but has the effect of diluting the accuracy of the initial data.

Several researchers and institutions have proposed and successfully applied Embodied Energy and the use of LCA as a practical method of measuring sustainability. These include: Chapas[8], Mayyas[9], Shuaib[10], ISO 14000 series[4-6] and Ashby[15]. This hard data is necessary when used at a detail level, e.g. redesigning products. The data also provides influence at higher levels e.g. management, regional, national and Global but the raw sustainability data requires modification and correlation with other influences to put it into context and become meaningful at the higher influence levels. For example, the increase in electric vehicles in an area might be influenced by: population increase, declining availability of gasoline, legislation reducing combustion engine emissions, etc. It is important therefore, to link influence levels with data collected at the product or design level and correlate the effect on decision making at those levels. Fig. 2 summarizes the nature of the sustainability measurements systems across the influence levels. The diagram is synthesized from reviews of the publications in Section 3. There are as many metrics as there are systems being measured, and measurement is complicated further when considering the end use of the data and its inevitable manipulation into an index format. As the intended use of the data becomes more global, greater manipulation is required to give a broader picture but this very action dilutes the data. The complexity of many measurement systems requires computing algorithms to produce viable data that can be used and directed for decision-making processes.

A matrix analysis in Fig. 3 is performed to investigate the relationship between the influence levels and various sustainability measurement systems. The references on the sustainability measurement are mapped in the matrix according to employed sustainability measurement systems for involved influence levels. Most references are distributed along the diagonal line to show the strong correlation between the sustainable measurement systems and the influence levels.

4.3 Integrated Sustainability Measurement Hierarchy (ISMH)

The whole sustainability measurement system is consolidated when four major features are cohesively combined. The diagram in Fig. 4 is the Integrated Sustainability Measurement Hierarchy (ISMH) derived from Figs. 2 & 3. The diagram provides a guideline and insight to help devise a comprehensive sustainability measurement system for better decisions in various influence levels.

The amalgamated sustainability measurement system consists of Triple Bottom Line (contextual overview), Life Cycle Analysis (detailed analysis and measurement), ISO Standards (guidelines for managing sustainability data and systems) and Metric of Embodied Energy.

The combination of these features creates a broad measurement system that can be used for single, and/or multiple component products. Guidance derived from the management strategy can influence components, departments, regions and global applications. For example, detail data can be derived by applying LCA and feeding the generated data upwards to the TBL level where influences cover economic as well as social aspects. Environmental data systems are prescribed by ISO standards and combined with other management standards providing a global network to other institutions.

The ISMH should be used as a guide for matching an appropriate sustainability measurement system against an influence level. Furthermore, it indicates from where measurement data can be gleaned for workers at a specific influence level. The hierarchy indicates precise boundaries for each influence level, but the complexity of sustainability measurements may mean that sometimes boundaries may be flexibly applied, depending on the project or the system being measured.

5. Conclusion

The evaluation of various frameworks and approaches to the application of sustainability revealed that many researchers are applying methodologies outside a cohesive model. This review combines the findings into an overall integrated hierarchy structure. The ISMH therefore helps the measurements to be taken at the detailed (product) level across the entire life cycle of a product or service or system, thus generating an energy accounting scheme. The ISMH also helps to create a feedback system enabling product improvement and a feed upwards system to the TBL intended for higher level decision making.

Acknowledgments

This study was supported by the Research Program funded by the SeoulTech (Seoul National University of Science & Technology).

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Fig. 1

The basic sustainability assessment model suggested by Ness[20]

Fig. 2

Nature of the sustainability measurement system across influence levels

Fig. 3

Analysis of correlation between sustainable measurement systems and influence levels